1. Field of the Invention
The present invention relates to a system for displaying a stored image within a display window of an already-displayed image such that the stored image may be easily scrolled. More particularly, the present invention concerns an image scrolling system which scrolls a stored image in a display window by 1) retrieving a portion of the stored image from a memory, 2) copying the portion to a video random access memory (VRAM) area, 3) displaying the portion in a display window corresponding to the VRAM area and 4) repeating steps 1) to 3) in response to operator-generated scrolling instructions.
2. Description of the Related Art
Conventional display systems are capable of scrolling an image in a window of a display screen. However, these systems must perform several complex steps to effect such scrolling. For example, applications written for the Microsoft Windows operating system scroll an image in a window by first moving still-visible portions of the image to their new position in the window. Next, the operating system issues a "paint" command instructing the application to redraw invalidated regions so as to fill any empty space in the window. The empty space is redrawn with second portions of the image such that the image appears to scroll in the window. Due to the complexity of these required steps, any scrolling performed by these conventional display systems is both time-consuming and computing-intensive.
Accordingly, what is needed is a display system for scrolling an image in a display window which reduces both computing time and VRAM.